$5xy - 7xz - x + 6 = 10y + 5$ Solve for $x$.
Combine constant terms on the right. $5xy - 7xz - x + {6} = 10y + {5}$ $5xy - 7xz - x = 10y - {1}$ Notice that all the terms on the left-hand side of the equation have $x$ in them. $5{x}y - 7{x}z - 1{x} = 10y - 1$ Factor out the $x$ ${x} \cdot \left( 5y - 7z - 1 \right) = 10y - 1$ Isolate the $x$ $x \cdot \left( {5y - 7z - 1} \right) = 10y - 1$ $x = \dfrac{ 10y - 1 }{ {5y - 7z - 1} }$ We can simplify this by multiplying the top and bottom by $-1$. $x= \dfrac{-10y + 1}{-5y + 7z + 1}$